This is a program project proposal. It requests support for nine individual projects. Each project will address some aspect of sleep and sleep disorders as a function of the aging process. Two large projects involving clinical sleep disorders form the core of the program. The first includes a precise, comprehensive assessment of the prevalence of sleep-wake disorders in discrete populations of elderly individuals. The core project involves a broad-based longitudinal assessment of elderly persons with sleep apnea syndromes and matched control subjects. The longitudinal study will evaluate mortality, morbidity, cardiovascular-respiratory function, cognition, behavioral function, and daytime alertness. Essential to the efficient progress of the two core projects are the installation and refinement of a sleep disorders information system and a series of microcomputer-based ammbulatory monitors. Another clinical project involves two key issues in hypnotic safety and efficacy in elderly patients; the effect of sleeping pills in individuals with sleep apnea, and the effect of sleeping pills on daytime alertness. Four additional projects will address basic research issues concerning sleep and aging. Circadian rhythms and aging will be evaluated using life span recordings of sleep-wake and activity-inactivity in mice. Nocturnal determinants of daytime alertness in elderly humans will be evaluated in a series of sleep restriction, sleep loss, and napping studies. The precise relationship of respiratory function during sleep to aging will be evaluated using sophisticated invasive procedures in cats. Finally, the fourth project will focus on neurochemical processes during sleep in the aging brain, with in vivo studies of young and old cats and dogs. A planning group, including epidemiologists, statisticians, gerontologists, and others will direct the project and integrate the research findings.